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Commercial wheat, corn and rice starch were extrusion cooked under a specific mechanical energy input (SME) ranging from 81 to 365 Wh/kg (288 to 1314 kJ/kg). Extrusion cooking at low and high SME resulted in products having significant differences in molecular weight distribution and having crystalline structures of the V-and E-type, as determined by gel permeation chromatography and X-ray diffraction analysis. Differential scanning calorimetry revealed that the glass transition temperature (T g ) of the extruded starches was independent of the botanical source, the degree of extrusion-induced molecular fragmentation and the formation of the V-and E-type crystalline structures. The obtained master curve, defined by the relationship between water content and T g of the amorphous starch, may be used as a predictive tool in modelling the extrusion process of starch or starch containing blends, especially with regard to the formation of the morphological structure and texture attributes of directly expanded products.

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